Bioadhesive composition and method of treatment therewith

ABSTRACT

A controlled release treatment composition and method of use are disclosed. The composition includes a bioadhesive and an effective amount of a treating agent. The bioadhesive is a water-swellable, but water-insoluble, fibrous, cross-linked carboxy-functional polymer containing (a) a plurality of repeating units of which at least about 80 percent contain at least one carboxyl functionality, and (b) about 0.05 to about 1.5 percent cross-linking agent substantially free from polyalkenyl polyether.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 690,483, filed Dec. 20,1984, now U.S. Pat. No. 4,615,697, which is a continuation-in-part ofapplication Ser. No. 551,295, filed on Dec. 14, 1983.

TECHNICAL FIELD

The present invention contemplates compositions for treatment of skinand mucus membrane, and particularly contemplates controlled releasecompositions and methods of treatment that include bioadhesives.

BACKGROUND ART

Controlled release of an active agent; i.e., release of the active agentover a period of time, has been a source for considerable researcheffort over the past twenty to thirty years. Exemplary of systems thatutilize controlled release of an active agent are microcapsulescontaining medicaments as are illustrated in U.S. Pat. Nos. 3,242,051and 3,041,289. Substantially inert plastic matrices containing an activeagent such as a pesticide dissolved or dispersed therein as areillustrated by U.S. Pat. Nos. 3,590,119, 3,639,583, and 4,012,221,exemplify yet another class of controlled release system.

Several materials, which in the presence of water adhere to the skinand/or mucus membranes, have been used by themselves or in conjunctionwith one or more active agents to treat various pathological conditions.Exemplary of such materials are the complex of sulfated sucrose andaluminum hydroxide known generically as sucralfate and available underthe trademark CARAFATE® from Marion Laboratories, Inc. of Kansas City,MO. Sucralfate is used alone or in conjunction with an antacid to treatduodenal ulcers. Another adherent material, designed for use in thebuccal cavity, is a combination of gelatin, pectin and sodiumcarboxymethylcellulose in a plasticized hydrocarbon gel available underthe trademark ORABASE® from Hoyt Laboratories Division ofColgate-Palmolive Co. of Needham, MA. A mucosal adherent ointment basedupon partly neutralized polymethacrylic acid methyl ester was recentlyreported by Bremecher et al., Arzneim.-Forsch./Drug Res., 33, 591(1983). That ointment was reported to show a pseudoplastic qualitywithout any thixotropic effect, good mucosal adhesion and no localirritation.

A sustained release compressed tablet is described in U.S. Pat. No.3,065,143. The tablet is reported to contain a medicinal agent and ahydrophilic gum that hydrates rapidly and swells in aqueous fluids atbody temperature. Several naturally occuring and synthetic gums are saidto be useful. Particularly useful gums disclosed include hydroxypropylmethyl cellulose ethers, sodium carboxy methyl cellulose, a materialdescribed as carboxy polymethylene, and mixtures thereof.

Delayed release pharmaceuticals are also disclosed in U.S. Pat. No.3,074,852. The compositions of this patent are disclosed to contain amedicinal component and a polymer carrier. The polymer carrier isdisclosed as being a polymer of U.S. Pat. No. 2,798,053, prepared bypolymerization of 0.75 to 2 percent by weight polyalkenyl polyether ascross-linking agent with acrylic acid, or its equivalent.

The polymerization is reported to be carried out in a hydrocarbondiluent with a free radical catalyst. The polymer of particular interestin U.S. Pat. No. 3,074,852 is said to be in acid form, and is moreparticularly described in U.S. Pat. No. 2,909,462, which patent furtherdescribes its polymers as being agglomerated by steam action. Thatparticularly described polymer is reported to be the material sold asCARBOPOL®934 by B. F. Goodrich Chemical Company.

U.S. Pat. No. 3,330,729 discloses tablets that contain a basic,pharmaceutically acceptable calcium or magnesium salt such as magnesiumoxide, calcium oxide or calcium hydroxide admixed with a medicament anda cross-linked acrylic acid polymer. The cross-linked polymer utilizedin those tablets is said to be described in U.S. Pat. No. 2,798,053, andcontains acrylic acid cross-linked with about 0.75 to about 2 percent byweight of the polymer of a copolymerized polyalkenyl polyether.Exemplary polyalkenyl polyethers are disclosed as polyallyl sucrose orpolyallyl pentaerythritol that are said to desirably contain an averageof at least 3 allyl groups per molecule, the allyl groups being bondedby ether linkages. The exemplary cross-linked polymer is again said tobe CARBOPOL®934.

U.S. Pat. No. 4,327,725 discloses an osmotic device that includes asemi-permeable wall surrounding a compartment housing (a) an agent(e.g., a drug) that is insoluble to very soluble in aqueous andbiological fluids, and (b) a layer of a fluid swellable, hydrogel. Alarge number of hydrogels are disclosed including neutral, anionic andcationic materials. The hydrogel is said to function in this device byimbibing an aqueous fluid, swelling, and thereby exerting a forceagainst the solution or suspension of the agent, whereby the agent isdispensed through the semi-permeable wall.

A controlled release system based on a neutral hydrogel of a polymer ofethylene glycol methacrylate or similar monomer cross-linkedsufficiently to make the polymer insoluble is disclosed in U.S. Pat. No.3,551,556. Example 8 of that patent also discloses an acid-containinghydrogel prepared by the copolymerization of methacrylic acid and maleicanhydride to form what appears to be a linear, noncross-linked polymer.Drug concentration from that hydrogel delivery system was reported tosoon reach a maximum and then decrease according to a flat, logarithmiccurve.

Drug-dispensing films are disclosed in U.S. Pat. No. 3,641,237. Thefilms of that patent are disclosed to be prepared by polymerization oflower alkoxy lower alkyl acrylates and methacrylates along with a 0-40percent of a hydrophilic acrylic monomer in the presence of across-linking agent. Various monomers are disclosed as useful for the0-40 percent co-monomers, including hydroxyalkyl acrylates andmethacrylates, salts of alpha,beta-unsaturated organic acids and strongacid salts of polymerizable ethylenically unsaturated amine-containingmonomers.

European Patent Office Publication No. A1 0 043 319 discloses copolymerscapable of absorbing and progressively liberating pharmaceuticallyactive substances. The useful copolymers are disclosed to contain about30 to 80 percent acrylate or methacrylate alkyl monoester, about 5 to 68percent acrylic or methacrylic acid and about 2 to about 15 percent of abi- or tri-functional acrylate or methacrylate ester. Exemplarybi-functional ester cross-linking agents are ethylene and polyethyleneglycol diacrylates. Trimethylolpropane triacrylate and triethylolpropanetrimethacrylate are exemplarly tri-functional esters.

U.S. Pat. No. 4,226,848 discloses a composition for adhering apharmaceutical preparation to the mucosa of the oral or nasal cavities.The composition disclosed contains a water-swellable and mucosa-adherentpolymeric matrix comprising (a) about 50 to about 95 percent by weightof a cellulose ether and (b) about 50 to about 5 percent by weight of ahomo- or copolymer of acrylic acid or a pharmaceutically acceptable saltthereof, with a pharmaceutically effective amount of a medicamentdispersed therein.

It is stated in that patent that when either material of the adherentcomposition is used singly in producing a pharmaceutical preparation,the resulting preparation is unsuitable as a slow-releasing preparationbecause it does not adhere to the mucosa of the oral or nasal cavity oreven when it adheres, it is relatively rapidly, disintegrated, dispersedor dissolved by the saliva or other secretions. The specified ratio ofthe two polymers that form the polymeric matrix is reported to beessentially required in order for the slow-releasing preparationdisclosed in that patent not to cause whitening of the mucosa and torelease the medicament at a controlled rate. It is further reported thatwhen the polyacrylic acid or salt portion of that composition is presentat greater than about 50 percent by weight, the preparation irritatesthe mucosa, and causes whitening of the mucosa and the marked occuranceof blisters thereon.

The polyacrylic acid or salt portion of the preparation of U.S. Pat. No.4,226,848 is also described as being water-soluble or water-swellable,but is further described as having a desired, specific range ofviscosities at a concentration of 0.2 percent by weight in water. Thus,if that polymer is not truly soluble in water, it is dispersible to atleast a sufficient extent to obtain the desired viscosity. An exemplaryacrylic acid polymer disclosed therein is the lightly cross-linkedacrylic acid-allyl sucrose copolymer available under the trademarkCARBOPOL®934 from B. F. Goodrich Chemical Co., which is said to form ahigh viscosity gel-like dispersion in water.

BRIEF DESCRIPTION OF THE INVENTION

The present invention contemplates controlled release compositions andmethods utilizing those compositions. The compositions include abioadhesive and an effective amount of a treating agent. The bioadhesivecomprises a water-swellable, but water-insoluble, fibrous, cross-linkedcarboxy-functional polymer. That polymer contains (a) a plurality ofrepeating units of which at least about 80 percent contain at least onecarboxyl functionality and (b) about 0.05 to about 1.5 percentcross-linking agent substantially free from polyalkenyl polyether, thepercentages being based upon the weights of unpolymerized repeatingunits and cross-linking agent, respectively. In typical practice, theratio by weight of the bioadhesive to the treating agent in thecomposition is about 200,000:1 to about 1:100.

The treating agent may be a medicinal agent such as an agent fortreating a cardiovascular condition, an agent for treating an internalcondition, an agent for treating a mental health condition, anantibiotic treating agent, a chemotherapeutic agent, ananti-inflammatory agent, a high molecular weight protein or polypeptidetreating agent, or the like. The treating agent may also be a cosmeticagent such as a sun screen, a skin softener, an acne treating agent, orthe like. The treating agent may also be a nutritional agent.

A composition of this invention may be provided in a variety of physicalforms. For example, a composition may be an intimate mixture of thebioadhesive and treating agent in either dry form, as a semi-solid or asa liquid suspension. The composition may also be provided as athree-dimensional structure such as a capsule, a capsule aggregate, afilm or laminate. When provided as a three-dimensional structure, thetreating agent is contained in a medicinally inert matrix and thestructure defines at least one surface on which the bioadhesive isdisposed.

The controlled release composition adheres to the skin or to mucusmembranes (mucosa) in the presence of sufficient water to swell thebioadhesive.

A controlled release method of treatment is also contemplated. Accordingto this method, a controlled release composition of this invention isprovided. An area of skin or of mucus membrane to be treated iscontacted with that composition, with the contacting being carried outin the presence of sufficient water to swell the bioadhesive. Thecomposition adheres to the area contacted, releasing the treating agentat a controlled rate, and causing the treating agent to be sorbed atleast at the vicinity of the contacted area.

The contacting step may be carried out by instillation of thecomposition in liquid form directly onto the area to be treated such asin the precorneal pocket of the eye. Contact between the composition andtreated area may also be carried out by swallowing the compositionwhereby the composition contacts mucosa of the gastrointestinal tract. Acomposition of this invention may also be inserted into the buccal,nasal, vaginal and/or anal cavities to contact the mucosa therein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures forming a part of this disclosure,

FIG. 1 illustrates a diagramatic side view of a modified, commerciallyavailable surface tensiometer utilized to measure adhesive strength ofbioadhesives;

FIG. 2 is a bar graph illustrating relative amounts of bioadhesiveremaining in the small intestine of laboratory rats into whose stomachsgelatin capsules containing the bioadhesive and a radioactive label weresurgically implanted;

FIG. 3 is an enlarged, diagramatic, fragmentary cross-sectional view ofa composition of this invention as a film;

FIG. 4 is an enlarged, diagramatic, fragmentary cross-sectional view ofa composition of this invention as a laminate;

FIG. 5 is an enlarged, diagramatic, fragmentary perspective view of anaggregate of a plurality of capsular compositions of this invention;

FIG. 6 is an enlarged, diagramatic, cross-sectional view of acomposition of this invention in capsular form taken along plane 6--6 ofFIG. 5;

FIG. 7 is another enlarged, diagramatic, fragmentary cross-sectionalview of a composition of this invention as a film;

FIG. 8 is another enlarged, diagramatic, fragmentary cross-sectionalview of a composition of this invention as a laminate;

FIG. 9 is a graph illustrating the in vivo concentration ofchlorothiazide in micrograms/milliliter (μg/ml) as a treating agent overa 30 hour period in the plasma of laboratory rats as dispensed from abioadhesive-albumin bead sustained release composition of this invention( ), from a control, albumin bead sustained release compositioncontaining no bioadhesive ( ), and from a control, bioadhesive-free,non-sustained release composition (□). Horizontally ended vertical linesat each datum point are error bars reported as standard error of themean;

FIG. 10 is a graph illustrating the force (dynes×10⁻² /cm²) fordetatching a bioadhesive polymer reaction product of acrylic acidcopolymerized with 0.3 weight percent 3,4-dihydroxy-1,5-hexadine havinga density of 1.56 grams/cubic centimeter (g/cc) versus pH value; and

FIG. 11 is a semilogarithmic plot showing of the percentage ofradiolabeled materials studied remaining in rat stomach versus time.Closed circles ( ) represent ⁵¹ Cr-labeled poly(acrylic acid/0.3 weightpercent 3,4-dihydroxy-1,5-hexadiene); density=1.56 g/cc; y=2.025-0.027x(r=-0.9937). Inverted triangles (∇) represent ⁵¹ Cr-labeledpoly(methacrylic acid/0.3 weight percent divinyl benzene); density=1.36g/cc; y=2.138-0.0745x (r=-0.9850). Open squares (□) representAMBERLITE®200 resin beads; density=1.53 g/cc; y=2.130-0.296x(r=-0.9960). Open circles ( ○) represent ⁵¹ Cr-normal saline;y=1.616-0.015x (r=-0.9971).

The present invention provides several advantages and benefits. Salientamong those advantages is the provision of improved controlled releaseof a treating agent to the skin or mucosa over an extended period oftime.

Another advantage of the present invention is that its compositions arenot noticeably irritating to the skin or mucosa with which they arecontacted.

One of the salient benefits of the present invention is that itstreating agent may be substantially any medicinal agent or cosmeticagent that is a solid at ambient temperatures.

Yet another benefit of the present invention is that its compositionsmay be fabricated with relative ease.

Still further benefits and advantages of the present invention will beapparent to those skilled in the art from the Detailed Description,Examples and claims that follow.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to controlled release compositions andmethods of their use. The compositions themselves include an effectiveamount of a treating agent and a bioadhesive.

The compositions are designed for use on the skin and mucus membranes(mucosa) of an animal body, such as that of a human, to which thecompositions adhere in the presence of a sufficient amount of water toswell the bioadhesive. The compositions so adhered to mucosa or skinslowly release the treating agent to the contacted body area forrelatively long periods of time, and cause the treating agent to besorbed (absorbed or adsorbed) at least at the vicinity of the contactedbody area. Such time periods are longer than the time of release for asimilar composition that does not include the bioadhesive as disclosedherein.

The compositions of this invention are substantially non-toxic to theanimals in which or on which they are placed, aside from any toxicityassociated with the treating agent alone. Thus, when contacted with andadhered to skin or mucosa, the compositions cause no apparent whiteningor blistering effects due to the bioadhesive. In addition, adverseimmunologic effects from the use of compositions of this invention inanimals have not been noted.

The treating agents useful herein are selected generally from theclasses of medicinal agents and cosmetic agents. Substantially any agentof these two classes of materials that is a solid at ambienttemperatures may be used in a composition or method of the presentinvention. Treating agents that are liquid at ambient temperatures, e.g.nitroglycerin, can be used in a composition of this invention, but arenot preferred because of the difficulties presented in theirformulation.

Exemplary medicinal agents include agents for treating cardiovascularconditions such as chlorothiazide (diuretic), propranolol(antihypertensive), hydralazine (peripheral vasodilator), isosorbide ornitroglycerin (coronary vasodilators), metoprolol (beta blocker),procainamide (antiarrythmic), clofibrate (cholesterol reducer) orcoumadin (anticoagulant); agents for treating internal conditions suchas conjugated estrogen (hormone), tolbutamide (antidiabetic),levothyroxine (thyroid conditions), propantheline (antispasmodic),cimetidine (antacid), phenyl propanolamine (antiobesity), atropine ordiphenoxalate (antidiarrheal agents), docusate (laxative), orprochlorperazine (antinauseant); agents for treating mental healthconditions such as haloperidol or chlorpromazine (tranquilizers),doxepin (psychostimulant), phenytoin (anticonvulsant), levo dopa(antiparkinism), benzodiazepine (antianxiety) or phenobarbital(sedative); anti-inflammatory agents such as fluorometholone,acetaminophen, phenacetin, aspirin, hydrocortisone, or predisone;anti-histamines such as diphenhydramine hydrochloride ordexchlorpheniramine maleate; antibiotics such as sulfanilamide,sulfamethizole, tetracycline hydrochloride, penicillin and itsderivatives, cephalosporin derivatives or erythromycin; chemotherapeuticagents such as sulfathiazole, doxorubicin, cisplatin or nitrofurazone;topical anaesthetics such as benzocaine; cardiac tonics such asdigitalis or digoxin; antitussives and expectorants such as codeinephosphate, dextromethorphan or isoproterenol hydrochloride; oralantiseptics such as chlor hexidine hydrochloride or hexylresorcinol;enzymes such as lysozyme hydrochloride or dextronase; birth controlagents such as estrogen; opthalmic treating agents such as timolol orgentamycin, and the like. In addition, medicinal treating agents mayalso include whole proteins such as the VP₃ capsid protein (also knownas the VP_(Thr) and VP₁ capsid proteins in other nomenclature systems)of foot-and-mouth disease virus described in U.S. Pat. No. 4,140,763 asbeing useful as the active ingredient in a vaccine againstfoot-and-mouth disease, insulin or interferon; polypeptide treatingagents such as endorphins, human growth hormone, or bovine growthhormone, or still lower molecular weight polypeptides or conjugates ofthose polypeptides linked protein carriers as are described in Sutcliffeet al., Science, 219, 660-666 (1983). Exemplary cosmetic agents includesun screens such as p-dimethylaminobenzoic acid or glycerylp-aminobenzoate, a skin softener such as urea, keratolytic agents suchas salicylic acid; acne treating agents such as benzoyl peroxide orsulfur; perfumes, and the like. Nutritional agents such as vitaminsand/or minerals like riboflavin and iron, respectively, may alsocomprise useful treating agents herein.

The treating agent may be used singly or as a mixture of two or moresuch agents.

One or more adjuvants may also be included with a treating agent, andwhen so used, an adjuvant is included in the meaning of the phrase"treating agent" as that phrase is used herein. Exemplary of usefuladjuvants are chelating agents such as ethylenediaminetetracetic acid(EDTA) that bind calcium ions and assist in passage of medicinal agentsthrough the mucosa and into the blood stream. Another illustrative groupof adjuvants are the quaternary nitrogen-containing compounds such asbenzalkonium chloride that also assist medicinal agents in passingthrough the mucosa and into the blood stream.

The treating agent is present in the compositions of this invention inan amount that is sufficient to prevent, cure and/or treat a conditionfor a desired period of time for which the composition of this inventionis to be administered, and such an amount is referred to herein as "aneffective amount". As is well known, particularly in the medicinal arts,effective amounts of medicinal agents vary with the particular agentemployed, the condition being treated and the rate at which thecomposition containing the medicinal agent is eliminated from the body,as well as varying with the animal in which it is used, and the bodyweight of that animal. Consequently, effective amounts of treatingagents may not be defined for each agent. Thus, an effective amount isthat amount which in a composition of this invention provides asufficient amount of the treating agent to provide the requisiteactivity of treating agent in or on the body of the treated animal forthe desired period of time, and is typically less than that amountusually used.

Inasmuch as amounts of particular treating agents in the blood streamthat are suitable for treating particular conditions are generallyknown, as are suitable amounts of treating agents used in cosmetics, itis a relatively easy laboratory task to formulate a series of controlledrelease compositions of this invention containing a range of suchtreating agents to determine the effective amount of such a treatingagent for a particular composition of this invention. While theeffective amount for all treating agents cannot be stated, typicalcompositions of this invention may contain about one microgram to aboutone gram of treating agent per dose administered. More preferably, acomposition of this invention may contain about one microgram to about250 milligrams per dose.

The second principle ingredient of the compositions of this invention isa bioadhesive. This bioadhesive comprises a water-swellable, butwater-insoluble, fibrous, cross-linked carboxy-functional polymer. Thepolymer contains (a) a plurality of repeating units of which at leastabout 80 percent contain at least one carboxyl functionality and (b)about 0.05 to about 1.5 percent cross-linking agent substantially freefrom polyalkenyl polyether, with the percentages being based upon theweights of unpolymerized repeating unit and cross-linking agent,respectively. In more preferred practice, at least about 90 percent ofthe repeating units contain at least one carboxyl functionality, and instill more preferred practice, at least 95 percent of those repeatingunits contain at least one carboxyl functionality. Most preferably, thebioadhesive is a reaction product of the polymerization of only acarboxyl-functional monomer and the cross-linking agent. Also in morepreferred practice, the bioadhesive contains about 0.1 to about 1percent by weight of polymerized cross-linking agent.

A bioadhesive may be broadly defined as a material that adheres to alive or freshly killed biological surface such as mucus membrane or skintissue. Bioadhesion as that phrase is used herein to define a usefulbioadhesive is assayed by a procedure described hereinafter in Example 2that measures the force required to separate two layers of freshlyexcised rabbit stomach tissue that are adhered together by an adhesive.Using this procedure, a bioadhesive may be defined as a material thatrequires a force of at least about 50 dynes/cm² to separate two adhered,freshly excised pieces of rabbit stomach tissue, following the procedureof Example 2. Upper limits for forces required to separate the freshlyexcised rabbit tissue are presently unknown, but are believed to be atleast about 2000 dynes/cm².

For purposes of comparison, a non-bioadhesive, cross-linked stronglyacidic, macroreticular and swellable polymer having sulfonic acidfunctionality such as the cation exchange resin sold by Rohm and Haas,Company of Philadelphia, PA as its AMBERLITE® 200 exchange resinrequires almost no force to separate the excised tissue, whilehomopoly(2-hydroxyethyl methacrylate) requires a force of about 29dynes/cm² for separation.

As noted previously, at least about 80 percent of the repeating units ofthe bioadhesive contain at least one carboxyl functionality. Exemplarymonomers that provide these repeating units are monoethylenicallyunsaturated and include acrylic acid, methacrylic acid, fumaric acid,maleic acid, maleic anhydride which may be hydrolyzed into its acid formduring or after polymerization, itaconic acid, crotonic acid, and thelike. Each of these acids may be used alone or in combination with othersuch acids or with one or more pharmaceutically or cosmeticallyacceptable salts of those acids. Acrylic acid is particularly preferredmonomer for providing the repeating units of the bioadhesive polymer.

The bioadhesive polymers of this invention are cross-linked bycross-linking agents as are known in the art. The cross-linking agent issubstantially free from polyalkenyl polyethers, and is particularly freefrom polyalkenyl polyethers such as polyallyl sucrose or polyallylpentaerythritol containing an average of at least three allyl groups permolecules as are reportedly present in CARBOPOL® 934. Exemplary ofuseful cross-linking agents are divinylbenzene, N,N-diallylacrylamide,3,4-dihydroxy-1,5-hexadiene, 2,5-dimethyl-1,5-hexadiene and the like.

The amount of cross-linking of the bioadhesive is of some import. Whenless than about 0.05 weight percent of an appropriate cross-linkingagent is present, the bioadhesive tends to become water-soluble, orwater-dispersible, thereby losing its desired water-insoluble,water-swellable, fibrous character that is important to the invention.When greater than about 1 percent cross-linking agent is present, thewater-swellability of the bioadhesive begins to decrease appreciably. Atcross-linking agent levels greater than about 1.5 percent, thewater-swellability is sufficiently decreased so as to make thebioadhesive lose its desired, functional characteristics.

The above amounts of carboxy-functional repeating units andcross-linking agent are used to define the bioadhesive, but specificallyrefer to the percentages of those predecessor, unpolymerized monomers inthe reaction mixture from which the bioadhesive is polymerized. Thesepre-polymerization amounts are utilized because of the great difficultyin analyzing the polymerized bioadhesive. Although the amounts refer tothe pre-polymerized monomers, it is believed that the bioadhesivescontain substantially similar amounts of those monomers in polymerizedform.

A bioadhesive polymer useful herein may thus be defined as a reactionproduct of the copolymerization of at least 80 weight percentmonoethylenically unsaturated carboxy-functional monomer and about 0.05to about 1.5 weight percent of a cross-linking agent free of polyalkenylpolyether. The remaining monomers that may be present to constitute 100percent by weight of the monomers are discussed below.

In addition to the above two ingredients, the bioadhesive polymer mayalso include polymerized monoethylenically unsaturated repeating unitssuch as C₁ -C₆ alkyl esters of one or more of the above-described acidssuch as hexyl acrylate, butyl methacrylate and methyl crotonate;hydroxyalkylene-functional esters of the above-described acids thatcontain a per molecule average of 1 to about 4 oxyalkylene groupscontaining 2-3 carbon atoms such as hydroxyethyl methacrylate,hydroxypropyl acrylate and tetraethylene glycol monoacrylate;methacrylamide, acrylamide and their C₁ -C₄ mon- and di-alkylderivatives such as N-methyl acrylamide, N-butyl methacrylamide andN,N-dimethyl acrylamide; styrene; and the like as are known in the artas being copolymerizable with the above described carboxylfunctionality-containing monomers and cross-linking agents. Thebioadhesive polymers most preferably are prepared from only themonoethylenically unsaturated carboxy-functional monomer and thecross-linking agent.

The bioadhesives useful herein may be prepared by conventional freeradical polymerization techniques utilizing initiators such as benzoylperoxide, azobisisobutyronitrile, and the like, are polymerized in anaqueous medium, and are not agglomerated by steam action. Exemplarypreparations of useful bioadhesives are provided hereinafter and mayalso be found in U.S. Pat. No. 3,202,577, whose disclosures areincorporated herein by reference.

The polymers described in U.S. Pat. No. 3,202,577 are reported thereinto be useful in treating diarrheal states. The disclosures of thatpatent are directed to the use of its polymers as bulking or dehydratingagents, and not as bioadhesives.

The bioadhesive useful herein is fibrous or particulate, and swellablein water, but is insoluble in water. Thus, the bioadhesive useful hereinmay be distinguished from those polymers of U.S. Pat. Nos. 3,074,852,3,330,729 and 4,226,848, described hereinbefore that utilize CARBOPOL®934. That polymer does provide adhesion as discussed herein, but iswater-soluble, making it less desirable, and is therefore excluded fromthe bioadhesives of this invention. Thus, CARBOPOL® 934 is said in U.S.Pat. No. 4,226,848 to be sufficiently water-soluble to provide ameasurable viscosity at a concentration of 0.2 percent by weight inwater. Contrarily, as illustrated hereinafter in the examples, thebioadhesives useful herein are prepared in aqueous solution and separatetherefrom after polymerization.

In addition, the polymers of U.S. Pat. Nos. 3,074,852, 3,330,729 and4,226,848 are cross-linked by a polyalkenyl polyether such as thetriallyl ether of sucrose or the triallyl ether of pentaerythritol. Thebioadhesives of the present invention are substantially free of suchcross-links, particularly of cross-links by agents having an average ofat least about three allyl groups per molecule.

Nevertheless, the fibrous, bioadhesive polymers of this invention areswellable in water; i.e., the polymer particles sorb water (adsorb orabsorb) and thereby become larger in size in the presence of water. Thewater used for that swelling, may be that provided along with thecomposition of the present invention or it may be that provided by thebody of the treated animal, such as by gastric fluid or by mucosalsecretions such as saliva.

The size of the bioadhesive particles has some effect upon thecompositions of this invention. It is apparent that the bioadhesiveparticles should not be so large that the composition cannot beadministered without undue difficulty. For example, if the compositionis to be swallowed, the bioadhesive particles must be sized to permitpassage of the composition to the stomach without impeding passage ofsubsequently ingested foods or liquids thereto. Similarly, when thecomposition is to be used in the eye, finely comminuted bioadhesiveparticles, e.g. sized to pass through a 100 mesh sieve screen (U.S.Standard Sieve Series), are utilized so that visual impairment of thetreated animal is minimized.

Typically, at the maximum, a useful bioadhesive is sized to pass througha sieve screen having a 10 mesh (U.S. Standard Sieve Series); i.e., a2000 micron opening. Preferably, the bioadhesive particles are sized topass through a 30 mesh sieve screen (U.S. Standard Sieve Series).Particles having a relatively small size swell more rapidly than doparticles having a relatively large size, and thus, a relatively smallsize is preferred for the particles. Bioadhesion measurements discussedbefore and in Example 2 hereinafter are carried out using a bioadhesivesized to pass through a 30 mesh sieve screen and be retained on a 40mesh sieve screen (U.S. Standard Sieve Series).

Bioadhesion has not been found to be a function of the molecular weightof the bioadhesive. Consequently, the bioadhesive may be ofsubstantially any molecular weight, so long as its adhesion in theadhesion test described hereinafter is at least about 50 dynes/cm².

As noted previously, the bioadhesives are polymerized in an aqueousmedium. In preferred practice that aqueous medium is a saturatedsolution of an alkaline earth metal salt such as magnesium sulfate. Thealkaline earth metal salt serves at least two functions. First, itincreases the density of polymerization medium so that the polymerizedbioadhesive floats on the surface of the aqueous medium and may beeasily removed therefrom. Second, the use of magnesium sulfate, inparticular, reduces the swelling of the bioadhesive in the aqueousmedium so that polymerization and recovery are faciliated. Bioadhesivestypically contain about 0.5 to about 1 percent of the alkaline earthmetal ion after several water rinsings of the polymer.

A particularly preferred bioadhesive that is commercially available isthat material sold under the designation Polycarbophil by A. H. RobinsCo. of Richmond, VA. The United States Pharmacopeia, 1980 edition,United States Pharmacopeial Convention, Inc., Rockville, MD, at page638, indicates that polycarbophil is a polyacrylic acid cross-lined withdivinyl glycol that has a residue on ignition of less than 4.0% andabsorbs about 60 times its original weight in test B under Absorbingpower.

Useful bioadhesive polymers of this invention were examined as to theirdensities, which are typically about 1.30-1.70 grams/cubic centimeter(g/cc). The cross-linking percentage was found to have a small effectupon the resulting density of illustrative, synthesized polymers as isshown in the Table below. Also shown in that Table is a somewhat greatereffect upon density that is observed for different starting monomers.

    ______________________________________                                        Densities of Useful Bioadhesives                                              Bioadhesive                  Density.sup.2                                    Monomer    Cross-linker  %-CL.sup.1                                                                            (g/cc.sup.3)                                 ______________________________________                                        acrylic acid                                                                             3,4-dihydroxy-                                                                              0.05    1.49                                                    1,5-hexadiene                                                      acrylic acid                                                                             3,4-dihydroxy-                                                                              0.30    1.56                                                    1,5-hexadiene                                                      acrylic acid                                                                             3,4-dihydroxy-                                                                              0.60    1.57                                                    1,5-hexadiene                                                      acrylic acid                                                                             3,4-dihydroxy-                                                                              1.20    1.62                                                    1,5-hexadiene                                                      acrylic acid                                                                             3,4-dihydroxy-                                                                              2.00    1.65                                                    1,5-hexadiene                                                      methacrylic                                                                              2,5-dimethyl- 0.3     1.47                                         acid       1,5-hexadine                                                       methacrylic                                                                              divinyl       0.3     1.36                                         acid       benzene                                                            ______________________________________                                         .sup.1 %CL = weight percent crosslinking agent based upon total               polymerizable monomers.                                                       .sup.2 Density of each polymer was determined in a 2 milliliter specific      gravity bottle at 25° C. Benzene of known density (0.874 g/cc) was     used at the medium.                                                           .sup.3 g/cc = grams per cubic centimeter.                                

The ratio by weight of bioadhesive to treating agent may be quite broad.Typically, the weight ratio of bioadhesive to treating agent is about200,000:1 to about 1:100. In preferred practice, however, the weightratio of bioadhesive to treating agent is about 1:10 to about 10:1.Those weigh ratios are determined using dry ingredients.

In addition to the treating agent and bioadhesive, the compositions ofthis invention may also contain pharmaceutically or cosmeticallyacceptable diluents and/or one or more materials present as amedicinally inert matrix. For example, a useful bioadhesive may becoated on the surface of a pill containing the treating agent andappropriate diluents to form the pill and thereby form a composition ofthis invention. Exemplary compositions containing a medicinally inertmatrix are discussed hereinafter. In addition, one or more lubricants,plasticizing agents, binders, vehicles, coloring agents, taste and/orsmell controlling agents, and the like may also be present.

The phases "pharmaceutically acceptable", "cosmetically acceptable","physiologically tolerable" and "medicinally inert" are used herein tomean that the material so described may be used for treatments in or onhumans or other mammals without causing ill effects, such as toxicity,blistering or whitening of mucosa or skin tissues, and that thosematerials are not themselves treating agents or bioadhesives, as thoseterms are used herein.

A composition of this invention may contain an intimate mixture of thebioadhesive and the treating agent. That intimate mixture may, forexample, be a mixture of dry solids, or of the treating agent dissolvedor suspended in a pharmaceutically or cosmetically acceptable(physiologically tolerable) carrier that also includes suspendedparticles of bioadhesive. The phase "intimate mixture" is used herein tomean that the components of the composition are mixed substantiallyuniformly so that none of those components is localized. A minor amountof agitation immediately prior to use may be required for some liquidcompositions of this invention to achieve an intimately mixed state whenused.

Illustrative of an intimate mixture of dry composition components is anadmixed powder formed from comminuted bioadhesive particles having asize sufficient to pass through a 40 mesh sieve screen and be retainedon a 60 mesh sieve screen (U.S. Standard Sieve Series) admixed withsimilarly or smaller sized particles of a treating agent such aschlorothiazide. (Hereinafter, when particles are sized to pass throughone screen and be retained on a second screen, as above, the size of thepassing screen mesh will be written first, followed by a virgule, "/",and then the size of the retaining screen mesh. Thus, the above passingand retaining screen mesh sizes are written "40/60".) The mixture may beprovided for treatment in tablet form or within a gelatin capsule andingested for treatment.

In another embodiment, the bioadhesive is swollen in an aqueous mediumcontaining the treating agent, and the treating agent is sorbed(absorbed or adsorbed) into or onto the swollen bioadhesive particles.After drying, the composition so prepared is provided for treatment asdescribed above. The word "dry" is used herein in relation to abioadhesive to mean that the bioadhesive does not adhere when touchedwith a finger within a rubber glove, and is substantially unswollen.

A bioadhesive may also be employed with suppositories for rectal orvaginal administration. In such embodiments, the bioadhesive may becoated on the surface of a treating agent-containing suppository or itmay be dispersed therein.

An aqueous dispersion of N,N-dimethylaminobenzoic acid and a bioadhesiveis illustrative of one embodiment of this invention wherein thecomposition contains the bioadhesive and treating agent in an intimatelymixed form in a cosmetically acceptable aqueous carrier.

In another illustrative embodiment, the treating agent and bioadhesiveare intimately mixed in an pharmaceutically acceptable aqueous carrierand may be used in eye. Here, the treating agent such as the sparinglysoluble anti-inflammatory agent fluorometholone is provided as asaturated solute in a pharmaceutically acceptable aqueous carrier. Thebioadhesive comminuted to a 40/60 mesh sieve screen size, and morepreferably to pass through a 100 mesh sieve screen (U.S. Standard SieveSeries) is added to the saturated fluorometholone solution to form acomposition of this invention. The composition so prepared may then beinstalled in the precorneal pocket of the eye to contact theconjunctival surface, and thereby provide contact of the controlledrelease treating composition to that mucus membrane.

The bioadhesive provides the dose rate-controlling medium of the abovecompositions. In more preferred embodiments, the rate of controlledrelease is provided primarily by a medicinally inert matrix, such as apolymer, that is also present in the composition. A composition of thisinvention that contains a treating agent in such a matrix may be in theform of a three-dimensional structure such as a film, a laminate, amicrocapsule or aggregate of microcapsules, each of which structures hasat least one surface portion on which the bioadhesive is disposed. Suchmore preferred embodiments are discussed hereinbelow.

Reference is made in the following discussion to embodiments of thisinvention illustrated in FIGS. 3 through 8. Identical or functionallyanalogous elements shown in those figures are designated by identicalreference numerals followed by a capital letter. One capital letter isused throughout each figure, except for FIGS. 5 and 6 wherein the samecapital letters are used.

It is to be noted that the figures discussed hereinbelow are not drawnto scale. As a consequence, the thicknesses of an illustrated film orlaminate layer, or a dimension of a bioadhesive particle or capsule arenot intended to represent the relative thicknesses or dimensions ofthose materials. Similarly, the number of bioadhesive particles and ofcapsules illustrated in each figure are intended as exemplary and maynot represent the actual relative numbers of such materials in astructure.

For purposes of clarity, the treating agent 14 is illustrated in FIGS. 3through 8 as discrete dots. It is to be understood, however, that thetreating agent may be dissolved in the matrix and thus not visible, orit may be suspended in the matrix as an insoluble solute, or it may bepartly dissolved and partly suspended in the matrix.

FIG. 3 illustrates an embodiment of this invention in the form of a filmand is designated generally by the reference numeral 10. The film 10contains a first medicinally inert matrix 12A that contains the treatingagent 14A. The film 10 defines at least one surface portion 16A, and asshown, also defines a second surface portion 18A. The bioadhesive 20A isdisposed on at least the first surface portion 16A, and a second amountof bioadhesive may also be disposed on the second surface portion 18A.

FIG. 4 illustrates another embodiment of this invention wherein thecomposition is in the form of a laminate generally designated by thereference numeral 100. In this embodiment, a first layer of the laminate12B comprising a first medicinally inert matrix contains the treatingagent 14B and defines a first surface 17B and a second surface 19B.

A second layer of the laminate 22B is comprised of a second medicinallyinert matrix, and defines a first surface 16B and a second surface 15B.The second layer 22B is adhered to the first surface 17B of the firstlayer 12B along the second surface 15B. The first surface 16B of thesecond layer 22B also defines the first surface portion of the laminateon which the bioadhesive 20B is disposed.

The embodiment 100 illustrated in FIG. 4 further includes a third layer24B comprising a third medicinally inert matrix and defining a firstsurface 23B and a second surface 25B. The first surface 23B of the thirdlayer is adhered to the second surface 19B of the first layer 12B. Thesecond surface 18B of the third layer 24B also defines a second surfaceportion (18B) of the three-dimensional structure (laminate). Asillustrated, the second surface portion 18B of the laminate 100 alsocontains a bioadhesive 21B disposed thereon.

Another embodiment of this invention is illustrated by the first andsecond layers of the laminate 100 of FIG. 4. In that embodiment, thethird layer 24B is absent and a second surface portion of the laminate,otherwise designated by the reference numeral 18B, is defined by thesecond surface 19B of the first layer 12B.

Still further embodiments of the invention may also be illustrated withreference to FIG. 4. In one such embodiment, the three-layered laminateis present as shown, but a bioadhesive is disposed on only the firstsurface portion 16B of the laminate; i.e., the bioadhesive 21B disposedon the second surface 18B of the laminate is absent. In still anotherembodiment, the two-layered laminate discussed in the paragraphimmediately above is provided with a bioadhesive 21B disposedadditionally on the second surface portion of the laminate.

Another embodiment of the invention is illustrated in cross-section inFIG. 6 and is generally designated by the reference numeral 200. In thisembodiment, the composition has a capsular, three-dimensional form.Here, a medicinally inert matrix 12C contains the treating agent 14C.The medicinally inert matrix 12C defines a first surface portion 16C ofthe capsule on which a bioadhesive 20C is disposed.

The capsules disclosed herein typically have an average largestdimension of about 1 nanometer to about 5000 microns. As such, thosecapsules having an average largest dimension of about 1 to about 999nanometers are referred to as nanocapsules, while capsules having anaverage largest dimension of about 1 micron (1000 nanometers) to about5000 microns are referred to as microcapsules. Nanocapsules may beprepared by following the teachings of Kreuter, Pharm. Acta Helv., 58,196 (1983). The microcapsules typically have an average largestdimension of about 50 to about 2500 microns, while nanocapsules havetypical average largest dimensions of about 50 to about 800 nanometers.

FIG. 5 illustrates an alternative form of the capsules 200 of FIG. 6,wherein a plurality of capsules 200 are adhered together to form acapsule aggregate generally designated by the reference numeral 200a.The capsule aggregate 200a is typically held together by the adhesionprovided by the bioadhesive particles. The aggregate may be comprised ofa single type of capsule that contains a single treating agent, or of aplurality of different types of capsules that contain one or moretreating agents.

Due to the relative ease or preparation of capsule aggregatecompositions 200a as compared to individual capsule compositions 200,capsule aggregate compositions 200a are typically utilized herein.Capsules comprised of a medicinally inert matrix surrounding a treatingagent, but lacking bioadhesive particles are also useful herein inadditional embodiments of the invention as is discussed hereinbelow.

In a film embodiment, such as that illustrated in FIG. 7 and designatedgenerally therein by the reference numeral 300, the treating agent 14Dis contained within capsules 26D similar to those of FIG. 6 designatedby the reference numeral 200, but lacking a bioadhesive analogous to thebioadhesive 20C of FIG. 6. The capsules 26D of the embodiment of FIG. 7are themselves contained in a film comprised of a first medicinallyinert matrix 12D. The first matrix 12D defines at least a first surfaceportion 16D of the film, and as shown, defines a second surface portion18D.

The bioadhesive 20D of this embodiment is disposed upon the firstsurface portion 16D. Of course, if desired, bioadhesive may also bedisposed upon the second surface portion 18D defined by the first matrix12D of film 300.

The laminate illustrated in FIG. 8 and designated therein generally bythe reference numeral 400 is analogous to the laminate 100 of FIG. 4,with the exception that the treating agent 14E is contained in capsules26E that are themselves contained in the first medicinally inert matrix12E. It is to be understood that further embodiments of the inventionanalogous to the two- and three-layered further embodiments discussed inrelation to FIG. 4 are also contemplated wherein a treating agentanalogous to agent 14E is contained in capsules analogous to thecapsules 26E of FIG. 8.

It is to be noted that a laminate of this invention is not intended tobe limited to a structure having two or three layers. Rather, thelaminate may contain about five or more layers. In addition, thelaminate may include more than one layer that contains a treating agent.The figures and the previous description illustrate and describerelatively simple laminates for purposes of easy understanding. It is tobe understood, however, that more complex, multi-layered structures thatembody the concepts illustrated and described herein are alsocontemplated.

For example, in yet another embodiment (not shown), a plurality oflayers of medicinally inert matrix, at least one of which contains atreating agent, may be prepared into a relatively thick laminate. Thelaminate so prepared may then be sliced into thin slices, as with amicrotome, such that the principal surfaces of the laminate are thecross-sectional surfaces. A bioadhesive may then be adhered to such across-sectional surface to prepare a composition of this invention asindividual particles or as a particle aggregate. Such a laminate, priorto the addition of bioadhesive, has an appearance similar to thecross-sectional view of a multi-layered cake.

A laminate of this invention is thus seen to define at least one surfaceportion on which a bioadhesive is disposed. That laminate contains aplurality of medicinally inert matrices in layers, each of which layersdefines a first surface and a second surface wherein the layer surfacesare in stacked relation, with surfaces of adjacent layers being adheredtogether. At least one of the medicinally inert matrix layers containsan effective amount of a treating agent, and a surface of one of thoselayers defines the at least one surface portion of the laminate on whichthe bioadhesive is disposed.

It is also to be noted that the capsules, films and laminates discussedand illustrated herein need not be monolithic, having a continuoussurface. Rather, if desired, a capsule, film and/or laminate of thisinvention may be foraminous and be pierced with a plurality of holes asto provide relatively more rapid release of the treating agent. Suchholes or pores are usually present in the microcapsules described in theexamples, and may extend through the three-dimensional structure, or mayextend only part way through or within such a structure.

The medicinally inert matrices discussed hereinbefore may be made frommaterials that are chemically the same or different. The chemicalidentity of the medicinally inert matrix of any layer or film isdependent upon the controlled treating agent release that is desired, asis known.

Exemplary useful medicinally inert matrices include cross-linked humanserum albumin or bovine serum albumin (BSA); cross-linked gelatin;poly(2-hydroxyethyl methacrylate) (hereinafter denominated p-HEMA);copolymers containing HEMA and monoethylenically unsaturated monomerssuch as those described hereinbefore as useful in the preparation ofbioadhesives and some of which are described in U.S. Pat. No. 4,028,295;C₁ -C₄ alkyl cellulose ethers and cellulose ethers containingsubstituted C₁ -C₄ alkyl groups such as ethyl cellulose andhydroxypropylmethylcellulose, respectively; ethylene-vinyl acetatecopolymers as are described in U.S. Pat. No. 4,166,111;ethylene:propylene:diene copolymers as are described in U.S. Pat. No.3,590,119; cross-linked elastomers as described in U.S. Pat. Nos.3,639,583 and 3,417,181, and the like.

The above-mentioned matrices typically provide the principalrate-controlling means of release of the treating agent. That releasemay be obtained by gradual dissolution of the matrix or by erosion ofthe matrix through a dispersion mechanism to thereby provide a freshsupply of treating agent to the site of treatment, or by leaching of thetreating agent from the matrix in the presence of water provided by thetreated animal. Many systems providing release of active ingredientsfrom a matrix over a period of time are themselves known, and such knownsystems in themselves are not a part of this invention. Rather, it isthe combination of such systems with a bioadhesive described herein toprovide an improved controlled release composition that forms a part ofthis invention.

The medicinally inert matrices comprising the films and laminate layersdescribed in relation to FIGS. 3-8 may each have a thickness in thosestructures of about 50 to about 3000 micons, and more preferably ofabout 100 to about 1500 microns. Where multiple layers of matrices areutilized it is preferred that each layer be less than about 1000 micronsthick, but those layers may provide a laminate having a thickness ofgreater than about 1000 microns. Where single matrix films are used, thethickness of such films is typically about 500 to about 1000 microns,although thicker films up to about 3000 microns are also useful.

The various adjacent layers of the beforedescribed laminates may beadhered to each other by the adhesive character provided by each layerto its adjacent neighbor. For example, the surfaces of adjacent layersmay be wet with solvent and then placed together so that the matricesinterdissolve or interdisperse to provide the adherence. The adjacentlayers of the laminate may also be adhered together by means of aseparate layer of adhesive placed therebetween.

The bioadhesive particles disposed upon at least one surface portion ofthe beforedescribed three-dimensional structures typically adhere tothose surfaces through their own adhesive properties, and are typicallydisposed upon that at least one surface portion in a wet, swollen,adhesive form. Wetting of the surface portion on which the bioadhesiveparticles are disposed softens many useful matrices and permits at leastpartial entrapment of the bioadhesive particles in the softened surface.

A method of controlled release treatment also constitutes an aspect ofthis invention. In accordance with this method, a controlled releasecomposition containing an effective amount of treating agent per dose isprovided, as described before. An area of skin or mucus membrane to betreated is contacted with the provided composition. The contact iscarried out in the presence of sufficient water to swell the bioadhesiveand cause the bioadhesive-containing composition to adhere to the areacontacted, as well as cause the controlled release of the treating agentin the vicinity of that contact.

The compositions of this invention may provide the intimate contactbetween the treating agent and the mucosa that is preferred for highmolecular weight treating agents such as proteins and hormones. Thesecompositions, through their bioadhesion, maintain the intimate contactfor extended periods of time to thereby increase the relativeconcentration of the treating agent in the vicinity of that contact.

Each of the beforedescribed compositions may be administered inaccordance with this method.

The compositions of this invention may be administered by several meansto provide the desired contact between the skin or mucus membrane andthe composition. For example, where the treating agent is a sun screen,the composition may be applied to the skin by rubbing the compositionover the skin area to be treated. Where the conjunctival mucosa are tobe contacted, the aqueous composition described above may be instilledinto the precorneal pockets of the eyes. Where the buccal, nasal, analand/or vaginal mucosa are to be contacted, the composition may beapplied by hand, forceps or other suitable instrument. Where the mucosaof the stomach and/or intestines are to be contacted, the composition istypically swallowed, or implanted surgically, and contact with the mucusmembrane is achieved by the contraction of the stomach or intestinesand/or by the carrying action provided by passage of gastric fluidstherethrough.

The composition is left in place (contact maintained) for a timesufficient for the treating agent to be released over a controlledperiod, and thereby provide its medicinal or cosmetic function to thetreated animal. In most circumstances, some unused, still active,controlled release composition and the remainder of the compositionadministered are eliminated from the body by a natural bodily mechanism,such as by dispersion or erosion caused by an aqueous body fluid such assaliva, tears, gastric fluid or vaginal secretions. In other instances,such as where the treating agent is contained in a medicinally inertmatrix such as an ethylene-vinyl acetate copolymer or cross-linkedelastomer that is ingested, the flushing action provided by the flow ofgastric fluids and stomach contractions ultimately results in excretionin the feces of any unused composition and of the remainder of theadministered composition.

BEST MODES FOR CARRYING OUT THE INVENTION Example 1

Bioadhesive Polymer Preparation

Bioadhesive polymers useful herein were prepared following the generalsynthetic procedure discussed immediately below. Specific bioadhesivepolymers made in accordance with the general procedure are illustratedin Table 1, hereinafter.

A solution containing 100 milliliters of distilled water and 800 gramsof magnesium sulfate (MgSO₄ -7H₂ O) was heated to reflux with agitation.A mixture of 1 gram of initiator dissolved in 100 grams of monomericcarboxy-functional repeating unit and the amount of cross-linking agentshown in Table 1 was added to the refluxing aqueous solution withcontinued stirring. The polymerizing composition so prepared wasagitated and heated to the temperature shown in Table 1 for the periodof initial polymerization and of post-polymerization curing.

At the termination of the curing time, the polymerized composition wasdiluted with 150 milliliters of distilled water heated to a temperatureof about 95° C. and then strained through a stainless steel sieve havinga 40 mesh screen (U.S. Standard Sieve Series). The strained bioadhesiveremaining on the screen was washed with one 1 liter portion of waterheated to a temperature of about 80° C. followed by five separate 1liter washings using tepid water. The washed bioadhesive so prepared wasthen dried in a forced air oven at a temperature of 90° C. for a periodof 48 hours.

The bioadhesives so prepared were then used as such or comminuted andsieved to provide a desired particle size.

                  TABLE 1                                                         ______________________________________                                        Bioadhesives                                                                  Carboxy-                                                                      functional                                                                            Cross-           Polymerization Conditions                            Repeating                                                                             Linking  Initi-  Poly.                                                Unit.sup.1                                                                            Agent.sup.2                                                                            ator.sup.3                                                                            Time.sup.4                                                                          T..sup.5                                                                            Time.sup.6                                                                          Yield.sup.7                        ______________________________________                                        (A)     (a) 0.2  (1)     15    95     2    83                                 (A)     (b) 1.0  (1)     25    95    18    67                                 (B)     (a) 1.0  (1)     30    95    48    53                                 (B)     (b) 1.0  (1)     30    95    48    87                                 .sup. (C).sup.8                                                                       (a) 1.0  (1)     --    65    24    11                                 .sup. (D).sup.8                                                                       (a) 0.2  (2)     20    95    72    10                                 (A)     (c) 0.2  (1)     10    95     4    98                                 (B)     (c) 0.2  (1)     10    95    20    93                                 ______________________________________                                         .sup.1 100 Grams of each of the following carboxyfunctional repeating         units was used: (A) = acrylic acid; (B) = methacrylic acid; (C) = itaconi     acid; and (D) = maleic anhydride.                                             .sup.2 The numerals of the Table indicate the number of grams of the          particular crosslinking agent used. The particular crosslinking agents        were: (a) = 3,4dihydroxy-1,5-hexadiene; (b) = divinyl benzene; and (c) =      2,5dimethyl-1,5-hexadiene.                                                    .sup.3 One gram of the following initiators was used: (1) = benzoyl           peroxide; and (2) = azobisisobutyronitrile.                                   .sup.4 Initial polymerization time in minutes.                                .sup.5 Temperature in degrees C. for initial polymerization and               postpolymerization cure.                                                      .sup.6 Postpolymerization cure time in hours.                                 .sup.7 Yield of dried bioadhesive based upon the weights of starting          materials and recovered bioadhesive.                                          .sup.8 A nitrogen sparge was used during polymerization as was deaerated      distilled water prepared by boiling distilled water for a period of 10        minutes.                                                                 

Although optimization of polymerization conditions is not reflected inthe data of Table 1, it can be seen from those data that thebioadhesives useful herein are easily prepared in useful quantities. Itis noted that the first bioadhesive listed in Table 1 has bioadhesionand other physical and chemical properties that are substantiallyidentical to the commercially available bioadhesive sold under thetrademark POLYCARBOPHIL by A. H. Robins Co. of Richmond, VA.

Example 2

Measurement of Adhesion

As noted previously, a bioadhesive of this invention is awater-insoluble, but water-swellable, fibrous, cross-linkedcarboxy-functional polymer that contains specified amounts of carboxylfunctionality and cross-linking agent. In addition, to that chemicaldefinition, a useful bioadhesive by definition must also exhibit anadhesion between two pieces of freshly excised rabbit stomach tissue ofat least about 50 dynes/cm² when measured under specified conditions.Those conditions and the apparatus utilized for that measurement aredescribed hereinbelow.

The apparatus utilized for these measurements is illustrated in FIG. 1.Basically, the apparatus is a standard, surface tensiometer as isavailable from Biolar Corporation, of North Grafton, MA that has beenmodified by removal of the du Nuoy loop and its replacement by anelongated linking arm 48 and an excised stomach tissue holding means 44.

Fresh stomach was obtained from rabbits and was carefully washed with asolution containing 0.9 weight percent sodium chloride in distilledwater (saline solution) to remove the contents. The stomach was placedin an aerated saline solution until used.

The tissue was cut into a round shape from the fundus part of thestomach and secured mucosal side out over a weighted container such as a15 milliliter scintillation vial using rubber band, as indicated by thereference numeral 40 of FIG. 1. The container 40 was placed into a 500milliliter beaker 42 containing gastric fluid. The beaker 42 was placedunder the scale portion of the modified tensiometer as illustrated inFIG. 1.

A separate portion of excised stomach tissue was separated into twolayers of smooth muscle; i.e., the external longitudinal layer and theinternal circular layer. A piece of the internal circular layer wasplaced mucosal side out over a No. 2 rubber stopper, and the tissue wassecured to the rubber stopper using an aluminum vial cap having auniform-sized opening of about 0.78 square centimeters. The aluminumvial cap is available from Wheaton Company of Millville, NJ. A holdingmeans in the form of screw eye was inserted into the opposite end of therubber stopper from that to which the tissue was secured. The rubberstopper containing the holding means and affixed tissue was placed in anaerated saline solution until used.

One hundred microliters of gastric fluid was added to 4 milligramsamples of each polymer whose bioadhesion was to be measured. One hourafter that addition, the swollen polymer was carefully spread over thetissue on the rubber stopper. Any excess of fluid was removed from thepolymer by blotting with a tissue paper. The rubber stopper with holdingmeans, tissue and polymer 44 was suspended from the scale so that itrested in the beaker of gastric fluid. When the polymer layer was at adepth equal to that of the tissue already in the container on vial 40,the scale was adjusted to zero using appropriate weights. The rubberstopper with holding means, tissue and polymer 44 was then suspendedover the tissue on the weighted container 40, and that container 40 waselevated to contact the polymer using the elevation means 46. Care wastaken to assure that the tissue on the container 40 touched only thepolymer.

The beaker was then slowly raised until the tissues came into contact,the contact being initiated by the weight of the rubber stopper (1.8grams). After one minute, the weight was removed, and the force requiredto separate the polymer from the tissue was measured. The force exertedto separate the layers of stomach tissue was increased at a constantrate of 10 milligrams per second in weight until the tissues separated.

One measurement was carried out within five minutes of contact betweenthe tissue and adhesive of rubber stopper 44 and the tissue of the vial40. Excised stomach tissue was affixed to either the vial or rubberstopper within 30 minutes of sacrificing the rabbit and is therebyconsidered to be freshly excised tissue.

Exemplary results using the above measurement technique are illustratedfor four useful bioadhesives in Table 2 hereinafter. The bioadhesiveswere prepared as described in Example 1 with the exception that 0.3weight percent of cross-linking agent was utilized. After thepreparation, the bioadhesives were sieved and particles having a 30/40mesh size (U.S. Standard Sieve Series) were used for these measurements.

                  TABLE 2                                                         ______________________________________                                        Bioadhesion Measurements                                                               Weight to   Force to                                                          Separate    Separate  Number of                                      Polymer.sup.1                                                                          Tissues.sup.2                                                                             Tissues.sup.3                                                                           Measurements                                   ______________________________________                                        1        855 ± 55 1061 ± 68                                                                            13                                             2        864 ± 56 1072 ± 68                                                                            12                                             3        876 ± 57 1086 ± 71                                                                            13                                             4        306 ± 45  380 ± 56                                                                             8                                             ______________________________________                                         .sup.1 Polymer 1 = polyacrylic acid crosslinked with                          3,4dihydroxy-1,5-hexadiene; polymer 2 = polyacrylic acid crosslinked with     2,5dimethyl-1,5-hexadiene; polymer 3 = polyacrylic acid crosslinked with      divinylbenzene; and polymer 4 = polymethacrylic acid crosslinked with         divinylbenzene.                                                               .sup.2 Weights are in milligrams ± standard error of the mean (S.E.M.)     .sup.3 Forces are reported in dynes/cm.sup.2 ± S.E.M.                 

Using the above measuring technique, p-HEMA commercially available fromAldrich Chemical Co. of Milwaukee, WI, required a force of 29 dynes/cm²to separate the tissues, while AMBERLITE® 200 cationic exchange resinavailable from Rohm and Haas Co. of Philadelphia, PA, required almost noforce to separate the tissues.

Example 3

Gastrointestinal Transit of a Bioadhesive

The following study illustrates the adhesion of a typical bioadhesivefto the mucosa of the gastrointenstinal tract of the rat. Chromium ionshave been found to bind to the bioadhesives and are not substantiallyabsorbed across biological membranes. Thus, radioactive chromium ions(⁵¹ Cr) were a convenient tag for the presence of the bioadhesive.

Commercially available polycarbophil, density=1.56 g/cc, (10 grams,30/40 mesh) was swollen in distilled water (50 milliliters) to which wasadded ⁵¹ chromic chloride (1 milliCurie). The resulting admixture wasagitated for a period of 24 hours.

The suspension was filtered, and the swollen bioadhesive was resuspendedin 600 milliliters of distilled water, stirred for several hours andfiltered again. The swollen bioadhesive was then suspended in gastricfluid without pepsin (pH 1.2, U.S.P.), stirred and filtered repeatedlyuntil no radioactivity was detected in the washing filtrate.

The ⁵¹ Cr-labeled bioadhesive so prepared was dried for 24 hours in ahot air oven and then sieved again to provide 30/40 mesh (U.S. StandardSieve Series) particles.

150 Milligrams of the ⁵¹ Cr-labeled bioadhesive were packed into No. 3hard gelatin capsules (Parke-Davis Division of Warner-Lambert Company,Morris Plains, NJ). The radioactivity of each capsule was measuredimmediately prior to administration using an Auto-Gamma ScintillationSpectrometer model No. 5236 (Hewlett-Packard Co., Palo Alto, CA).

Male Sprague-Dawley rats weighing between 150 and 200 grams each werefasted for 48 hours, with free access to water, prior to administration.Each animal was anesthetized by placing it into a covered vessel havinga gauze pad saturated with ether (Anesthetic grade, Mallinckrodt, Inc.Paris, KY) attached to its inside surface. The animal was kept in thechamber for about three minutes, promptly removed, and secured on asurgical board with adhesive tape in the supine position after trimmingits abdomimal hair with animal clippers. The peritoneum was opened witha longitudinal incision about two centimeters in length.

The stomach was located and carefully removed intact from abdominalcavity with a forceps, and an opening two to three millimeters indiameter was cut into the fundus with surgical scissors. A preparedgelatin capsule containing Cr⁵¹ -labeled Polycarbophil was placed in thestomach through the opening so made.

The opening was then tied shut with a loop of sutures [3-0 silk (2metric) silicone treated nonabsorbable surgical sutures, U.S.P. Davisand Geck, Inc. Manati, PR], and tied in a square knot.

The stomach was replaced into the abdominal cavity and four millilitersof normal saline was injected into it using 271/2 G needle. The externalincision was closed with three or four sutures made with an eye needle(stainless steel, 706-1 eye needle, 3/8 circle, cut edge; The TerringtonCo., Terrington, CT) in both the peritoneium and epidermis.

The animal was placed in a cage and allowed to recover.

The procedure was done in about five minutes. Anesthesia was maintainedas needed by using a 50 milliliter beaker containing an ether-moistenedgauze pad placed over the nose of the rat.

After a predetermined time period, each rat was removed from its cage,placed into the ether chamber for anesthesia, and sacrificed. Theperitoneal cavity was opened and the stomach was carefully removed afterclamping both of the cardiac and pyrolic junctions of the stomach. Theexcised stomach was carefully placed in the bottom of a gammascintillation counting vial (15×30 millimeters, Packard test tubes forgamma counting Model #6001122).

The radioactivity of the counting vial containing a stomach was measuredusing the above Gamma scintillation counter.

Table 3, below, shows the amount of ⁵¹ Cr-labeled bioadhesive remainingin the rat stomachs at various times after insertion of the gelatincapsules. It can be seen that the bioadhesive remains in the stomach fora period of about 17-24 hours.

                  TABLE 3                                                         ______________________________________                                        Retention of Bioadhesive in Rat Stomachs                                                 Number   Percent of Bioadhesive                                    Time.sup.1 of Rats  Retained in the Stomachs.sup.2                            ______________________________________                                        1          6        .sup. 96.86 ± 1.15.sup.a                               2          5        91.30 ± 2.52                                           4          5        84.79 ± 2.42                                           6          4        78.31 ± 1.50                                           10         5        54.60 ± 1.00                                           17         5        37.00 ± 3.40                                           24         5         9.00 ± 3.20                                           ______________________________________                                         .sup.1 Time in hours after insertion of gelatin capsules.                     .sup.2 Percent ± S.E.M.                                                    .sup.a mean ± standard error of the mean.                             

A repeated, similar study showed similar results for retention of the ⁵¹Cr-labeled bioadhesive in the stomach. In that study, the smallintestines of the rats were also excised and cut into 20 approximatelyequal lengths. The radioactivity remaining in each of those lengths ofintestine was then counted following the above-discussed procedures.

The results from the study of retention of the bioadhesive in each ofthe 20 segments of the small intestine are shown graphically in FIG. 2from left to right in the direction from stomach toward the colon. Thetotal percentage of the administered bioadhesive present in the smallintestine is shown by the numerals above each graph. The areas undereach portion of the graph are proportional to the amount of bioadhesivein that segment of small intestine. Examination of the graph shows thechange in distribution from the stomach-end of the intestine toward thecolon-end.

Another, similar, stomach-empyting determination was conducted using abioadhesive prepared from methacrylic acid cross-linked withdivinylbenzene, density=1.36 g/cc, and shown as Polymer 4 of Table 2.The results of that determination are shown below in Table 4.

                  TABLE 4                                                         ______________________________________                                        Retention of Bioadhesive in Rat Stomachs                                                 Number   Percent of Bioadhesive                                    Time.sup.1 of Rats  Retained in the Stomachs.sup.2                            ______________________________________                                        2          5        82.25 ± 3.79                                           4          7        65.71 ± 4.96                                           6          7        62.50 ± 3.91                                           8          5        33.89 ± 5.55                                           16         5         8.28 ± 2.74                                           ______________________________________                                         .sup.1 Time in hours after insertion of gelatin capsules.                     .sup.2 Percent ± S.E.M.                                               

As can be seen from a comparison of the data in Tables 3 and 4, and thedata in Table 2, the methacrylic acid-divinylbenzene bioadhesive is lessadherent to the stomach mucosa than is polycarbophil or a bioadhesivewith similar adhesion properties to polycarbophil. Nevertheless, thedata for the control determinations discussed hereinbelow illustratethat both bioadhesive provide a substantial improvement in the timerequired for the stomach to empty its contents.

In one control determination, 1 milliCurie of ⁵¹ chromic chloride wasadded to 50 milliliters of normal saline solution and mixed thoroughly.Four milliliters of that mixture were injected into the stomachs of ratsfollowing the surgical procedure described before.

The radioactivity contained in each solution was measured prior toadministration. The rats were sacrificed after selected time periods,and the amount of radioactive solution remaining in the stomachsisolated from those rats was determined using the above scintillationcounter. The results of this determination are shown in Table 5, below,as the percentage of originally injected ⁵¹ chromic chloride solutionremaining in those stomachs.

                  TABLE 5                                                         ______________________________________                                        Amount of .sup.51 Cr-Normal Saline Solution                                   Remaining in Rat Stomachs                                                              Number   Percent of .sup.51 Cr-Normal Saline                         Time.sup.1                                                                             of Rats  Retained in the Stomachs.sup.2                              ______________________________________                                         5       5        37.3 ± 4.40                                              10       5        26.6 ± 5.10                                              20       5        20.3 ± 2.50                                              30       5        14.7 ± 1.50                                              60       5         5.0 ± 0.90                                              ______________________________________                                         .sup.1 Time in minutes after injection.                                       .sup.2 Percent ± S.E.M.                                               

Cationic exchange resin beads were used as exemplary ofnon-bioadhesive-containing microcapsules to determine the time requiredfor such microcapsules to be emptied from the stomach.

AMBERLITE®200 exchange resin beads, density=1.53 g/cc were sieved toprovide 30/40 mesh (U.S. Standard Sieve Series) particles. 150Milligrams of the beads were packed into clear, hard gelatin capsulesafter counting the number of beads in each capsules. Approximately 2880beads were contained in each capsule.

The gelatin capsules so prepared were surgicially implanted into ratstomachs as described previously. The animals were sacrificed at varioustimes after implantation as described, and the stomachs ware carefullyremoved and opened with a surgicial scissors. The beads present in eachstomach were then counted. The results of this determination, expressedas a percentage of the number of beads implanted per animal, are shownin Table 6, below.

                  TABLE 6                                                         ______________________________________                                        Amount of Exchange Resin Beads                                                Remaining in Rat Stomachs                                                                Number   Percent of Beads                                          Time.sup.1 of Rats  Retained in Stomachs.sup.2                                ______________________________________                                        1          5        95.80 ± 1.90                                           2          6        62.40 ± 3.30                                           3          4        26.75 ± 5.40                                           4          4        11.80 ± 3.50                                           6          5         3.60 ± 1.20                                           8          5         3.80 ± 1.20                                           ______________________________________                                         .sup.1 Time in hours after insertion of gelatin capsules.                     .sup.2 Percent ± S.E.M.                                               

It can thus be seen from the above data, and the data of FIGS. 2 and 11that illustrate intestinal transit of bioadhesive and stomach retentionof bioadhesive and controls, respectively, that the bioadhesives usefulherein are particularly adherent to the stomach and intestinal mucosa.These data also suggest that compositions containing these bioadhesivesand a treating agent as described herein are also similarly adherent.

Example 4

Bioadhesive-Coated Bovine Serum Albumin Microcapsules

The diuretic and anti-hypertensive drug chlorothiazide suffers from thedisadvantage of being poorly sorbed from the gastrointestinal tract andinto the blood stream. As a consequence of its relatively low sorption,much of the dosage administered orally, by pill, is excreted prior tothe treating agent being sorbed and used by the body. This drug istherefore frequently prescribed to be taken more than once per day. Itwould therefore be beneficial if the effect of a single dose could beprolonged and if a greater percentage of the treating agent per dosecould be sorbed.

Microcapsules containing chlorothiazide[6-chloro-2H-1,2,4-benzothiadiazine-7-sulfonamide 1,1-dioxide (1)] andhaving a surface coating of a bioadhesive useful herein were prepared asa composition of this invention. The procedures of Lee et al., Science,213, 233 (1981) and Royer et al., J. Parenter. Sci. Technol., 37, 34(1983) were followed in modified form for this preparation.

Two hundred milligrams of bovine serum albumin (fraction V, powder;Sigma Chemical Co., St. Louis, MO) (BSA) were dissolved in each of sixtest tubes, each tube containing of 1 millimolar phosphate buffer (pH7.5) at a temperature of 0°-4° C. 100 Milligrams of chlorothiazide (lot#L311,040-00N55; Merck Sharp & Dohme Research Laboratories, Rahway, NJ)was then suspended in each albumin solution. Cross-linking of the BSAwas initiated by the addition of 160 microliters of a 25 percent byvolume solution of glutaraldehyde (Grade II, Sigma Chemical Co.) to eachsuspension. This resulted in a final glutaraldehyde concentration of 4percent by volume in each solution.

Each suspension so prepared was agitated by vortex mixing, and thecontents of each test tube were separately and immediately injected intoa stirred oil phase using a 1 milliliter syringe fitted with a 20 Gneedle. The oil phase consisted of 110 milliliters of petroleum ether,90 milliliters of CCl₄ and 1 gram of sorbitan monoleate and was stirredat a rate of 120 revolutions per minute (rpm). Stirring was continuedfor about one hour after which time the microcapsules so produced werewashed 3 times with 50 milliliter portions of petroleum ether, dried ina vacuum dessicator for about 16 hours and then sieved to provide afraction having a 10/20 mesh size (U.S. Standard Sieve Series); i.e.,about 840 to about 2000 microns in largest dimension.

Equal masses of the microcapsules so prepared and polycarbophil [sievedto provide an 80/100 mesh (U.S. Standard Sieve Series) sized particles]were provided. The polycarbophil was allowed to swell in an excess ofdeaerated distilled water (Example 1). After swelling, the microcapsuleswere added to the swollen bioadhesive and the admixture so prepared wasmixed thoroughly by hand. The resulting mixture was poured onto analuminum dish and dried in an oven at a temperature of 70° C. forseveral hours.

The dry, hardened mass was scraped off of the dish with a spatula. Thebioadhesive-coated microcapsules and aggregates thereof so produced andconstituting compositions of this invention were of variously sizedparticles. Those particles were then loaded into No. 3 gelatin capsulesfor use in oral administration or administration by surgical implacementinto the stomachs of animals.

As far as can be determined, substantially all of the chlorothiazide,BSA and polycarbophil were contained in the ultimately producedcomposition. Thus, the ratio by weight of bioadhesive to treating agentin this composition was about 3:1 (1 part treating agent+2 parts BSA+3parts bioadhesive).

Example 5

Bioadhesive Coated Gelatin Microcapsules

128 Grams of distilled water at a temperature of about 55°-60° C. wereadmixed with agitation with 38 grams of gelatin. After standing at roomtemperature for 24 hours, the gelatin had dissolved (swollen) completelyto form a solution. The gelatin solution was then refrigerated at atemperature of about 2°-5° C. for a further 24 hour period.

The hard gel resulting from the refrigeration step was cut into smallcubes using a scissors. 12 Grams of sulfamethizol (SM) were admixed withthe gelatin cubes, and the resulting admixture was warmed with stirringat 200 rpm for 20 minutes in a water bath heated to a temperature ofabout 55°-60° C. The warmed admixture was then poured into 300 grams ofmineral oil that was previously heated to a temperature of about 55°-60°C. The mineral oil suspension was stirred at 200 rpm for a period of 5minutes, and then the vessel containing that mineral oil suspension wasplaced into an ice-water bath and its contents were quickly cooled to atemperature of less than about 5° C. The cooled suspension was stirredat 300 rpm and stirring was continued for 90 minutes while maintainingthe suspension temperature at about 5° C. until the gelatinmicrocapsules so produced had gelatinized substantially completely.

150 Grams of isopropanol at a temperature of 5° C. were added todehydrate the gelatinized microcapsules and the isopropanol-containingsuspension was stirred for an additional 30 minute period at 300 rpm.The dehydrated microcapsules were collected by filtration, washed threetimes with 60 gram portions of isopropanol cooled to a temperature ofabout 5°, and then dried using a hand-held hair drier set at its lowesttemperature until the odor of isopropanol was no longer detectable.

One gram of the microcapsules so prepared was then immersed in 10milliliters of 10 volume percent formalin-isopropanol in a covered glassvessel. The suspension so prepared was then refrigerated at atemperature of about 2°-5° C. for a period of 24 hours. The cross-linkedgelatin-SM microcapsules so prepared were washed in isopropanol and thendried. The microcapsules so prepared had an average longest dimension ofabout 1 to about 1000 microns.

If desired, microcapsules prepared as described above may be coated witha bioadhesive or intimately mixed with a bioadhesive to provide acomposition of this invention as discussed in Example 4.

Example 6

Bioadhesive Laminate Composition

A dispersion was prepared that contained 750 milligrams of sulfanilamideas treating agent, and 600 milligrams of ethyl cellulose as amedicinally inert polymer matrix in 8 milliliters of a solventcontaining a 7:2 by volume mixture of toluene and ethanol. 150Milligrams of castor oil as a plasticizer were added, and the resultingdispersion was homogenized and cast onto an aluminum dish to provide afilm having an area of 23.75 cm² and a thickness of 564-23 microns afterdrying.

400 Micrograms of poly(2-hydroxyethyl methacrylate) (p-HEMA, Example 2)were dissolved in 3 milliliters of dimethylformamide (DMF). Theresulting solution was poured into a glass petri dish and dried toprovide a film. The dry film so prepared had an area of 23.75 cm² and athickness of 168±8 microns. A second, substantially identical film wasalso prepared.

Two preparations of swollen polycarbophil were made using bioadhesiveparticles of 30/40 mesh (U.S. Standard Sieve Series) size. For eachpreparation, 160 milligrams of bioadhesive were swollen in a solutioncontaining 0.5 milliliters of DMF and 1.5 milliliters of distilledwater.

One side each of the above to p-HEMA films was wetted by a fine spray ofDMF. One minute thereafter, the above swollen bioadhesive particles wereevenly spread over the surface of each of the wet films using a spatula.The bioadhesive-coated p-HEMA films were then dried at room temperature.

The non-bioadhesive-coated surfaces of the p-HEMA films were wetthoroughly by spraying with DMF. Both surfaces of thesulfanilamide-containing ethyl cellulose films were also wet by sprayingwith DMF.

One wet surface of the sulfanilamide-containing ethyl cellulose film wasthen contacted with the wet surface of each of the p-HEMA-bioadhesivefilm to form a laminate composition of this invention. After drying atroom temperature, the laminate composition so prepared was cut intorectangular pieces about 2×3 millimeters on a side. The laminate piecesso prepared were loaded into gelatin capsules for oral administration.

The three-layered laminate prepared above contained a bioadhesive totreating agent weight ratio of about 1:2.3.

If desired, the second p-HEMA-bioadhesive film may be eliminated fromthe above composition to provide another alternative two-layeredlaminate composition of this invention, or one of the coatings ofbioadhesive may be eliminated to provide an alternative three-layeredlaminate composition of this invention. In addition, the swollenbioadhesive may be applied directly to one or both sides of the wet,sulfanilamide-containing ethyl cellulose film to provide still anothercomposition of this invention in film form. These alternativecompositions having bioadhesive disposed on only one surface portioncontain a bioadhesive to treating agent weight ratio of about 1:4.7.

Example 7

Bioadhesive Film Composition

3.36 Grams of p-HEMA (Example 2) as medicinally inert matrix weredissolved in 13 milliliters of dimethyl formamide (DMF), and 1.44 gramsof sulfamethiazole as treating agent were admixed with the resultingsolution. The treating agent-matrix solution was poured into a glasspetri dish having an area of 63.585 cm² and dried to form a film. Thefilm so prepared had a thickness of 1000±100 microns.

430 Milligrams of polycarbophil sieved to a 30/40 mesh size were swollenin 6 milliliters of a solution that contained 3 parts of water and 1part of DMF, by volume. The above-prepared film was wetted by a finespray of DMF. About one minute thereafter, the swollen bioadhesive wasevenly spread over the wet surface of the film using a spatula. The filmcomposition of this invention so prepared was then dried at roomtemperature.

After drying, a second, similar amount of bioadhesive was spread overthe second surface of the film composition to form another compositionof this invention. The second composition was dried again at roomtemperature and then cut into rectangularly shaped pieces havingdimensions of about 2×3 millimeters. Those pieces were thereafter loadedinto a gelatin capsule for use in oral administration.

The weight ratio of bioadhesive to treating agent in the first-describedlaminate of this Example was about 1:3.3, while the similar weight ratiofor the second-described laminate was about 1:1.7.

Example 8

Gelatin Microcapsule-Containing Laminate Compositions

The sulfamethiazole-containing microcapsules of Example 5 were utilizedto prepare a laminate composition of this invention. 100 Milligrams ofthose microcapsules were dispersed in a solution containing 250milligrams of p-HEMA (Example 2) in 4 milliliters of DMF.

That dispersion was poured into a glass petri desh having an area of23.5 cm² and then dried to provide a film having a thickness of 400-500microns. Two- and three-layered laminates of this invention havingbioadhesive disposed on one and two surface portions, respectively, wereprepared following the procedure of Example 6. Additional laminatecompositions of this invention that contain a microencapsulated treatingagent such as that of this Example can be prepared as is also discussedin Example 6.

Example 9

Rat Serum Treating Agent Levels

Microcapsules having BSA as an encapsulating medicinally inert matrixand chlorothiazide as treating agent were prepared by using ten timesthe amounts of reagents described in Example 4. The total amount of oilphase was the same as that used in Example 4, but 105 milliliters ofpetroleum ether and 95 milliliters of CCl₄ were used here.

More specifically, one gram of chlorothiazide (DIURIL®, Merck, Sharp &Dohme, Rahway, N.J.) was dispersed in 8.4 milliliters (ml) of a 2.4weight percent solution of bovine albumin (Fraction V powder, Sigma, St.Louis, Mo.) in 1 millimolar phosphate buffer (pH 7.5) maintained in anice bath. Crosslinking of the albumin was initiated by the addition of1.6 ml of 25 percent by volume aqueous solution of glutaraldehyde (GradeII, Sigma, St. Louis, Mo.), resulting in a final glutaraldehydeconcentration of 4 percent by volume. The dispersion was then quicklyvortexed, drawn into a 20 cc syringe, and immediately injected into astirring (120-150 rpm) oil phase consisting of 105 ml petroleum ether,95 ml carbon tetrachloride, and 1 g Span 80 (sorbitan monoleate).Stirring was continued for about one hour; the beads formed were thencollected and washed with about 50 ml petroleum ether over suction,dried in an oven at 70° C. for about two hours, and sieved to a 30/40mesh cut.

Albumin beads free from chlorothiazide (blank beads) were prepared bythe same method except that no drug was used.

The albumin beads were characterized with respect to drug content anddensity. The percent chlorothiazide in the beads was determined asfollows. A weighed amount of albumin beads was placed in a measuredvolume of dimethylformamide, and was shaken for 24 hours on a mechanicalshaker. An aliquot of the supernatant was then diluted appropriately andits absorbance was determined on a spectrophotometer (559A UV/VIS,Perkin-Elmer, Norwalk, CT) at 330 nanometers (nm) against adimethylformamide blank. The concentration of chlorothiazide wasinterpolated from a standard curve, and was converted to percent (wt/wt)chlorothiazide in the ablumin beads.

The approximate density of the beads was determined by the displacementmethod using a Weld pycnometer.

The albumin beads and polycarbophil (lot #AHR 3260, CH #13430, A. H.Robins Co.) were separately sieved to provide 30/40 mesh (U.S. StandardSieve Series) particles. The particles so sized were then loaded intogelatin capsules in a ratio by weight of albumin beads:polycarbophil of3:7 to provide an intimate mixture.

Male Sprague-Dawley rats weighing between 150 and 200 grams were fasted,with free access to water, for 36 to 48 hours prior to in vivodeterminations. The animals were anesthetized, and gelatin capsules and4 milliliters of normal saline were implanted and injected,respectively, into their stomachs as described in Example 3.

Number 4 gelatin capsules were used for these determinations. Thecapsules contained either 30 milligrams of albumin-chlorothiazine beadsplus 70 milligrams of polycarbophil (study) as a composition of thisinvention, 30 milligrams of albumin-chlorothiazine beads plus 70milligrams of blank beads (control I), or 9.5 milligrams ofchlorothiazine powder (Control II).

The implant bearing rats were caged for recovery. Thereafter, the ratswere removed from their cages at various times and placed in the etherchamber for about five minutes. Three to four milliliters of blood werecollected by cardiac puncture using a 22 G needle and a 5 millilitersyringe previously wet with heparin.

The collected blood was transferred to a 4 milliliter heparinized bloodcollection tube (VACUTAINER available from Becton-Dickinson, Rutherford,NJ) and immediately centrifuged (DYNAC centrifuge, Clay Adams,Parsippany, NJ) for 15 minutes at about 2000 rpm. The plasma so obtainedwas removed and stored at -20° C. until analyzed for its chlorothiazidecontent.

The concentration of chlorothiazide in the plasma was determined by thehigh pressure liquid chromatographic (HLPC) method of Burbhaiya et al.,J. Pharm. Sci., 70, 291 (1981).

In accordance with that method, 50 microliters of a 40microgram/milliliter solution of hydroflumethiazide (BristolLaboratories, East Syracuse, NY) as internal standard were added to 1.0milliliter of plasma along with 40 milliliters of toluene. After shakingfor 10 minutes and 3 minutes of centrifugation, the toluene layer wasaspirated and discarded.

To the remaining plasma solution were added 0.5 milliliters of 0.01molar acetate buffer (pH 3.8) and 5.0 milliliters of ethyl acetate.After shaking for 10 minutes and centrifugation for 3 minutes, 4.0milliliters of the ethyl acetate layer were transferred to a clean tube,and evaporated to dryness under a gentle stream of nitrogen. The driedmaterial so obtained was reconstituted with 75 microliters of methanol,and 20 microliters of the resulting methanol solution were injected intothe HPLC column.

The HPLC system consisted of a solvent pump (Model 110A, AltexScientific, Berkeley CA), a 20 microliter, fixed volume injection valve(Model 210, Altex Scientific), a 10 micron particle size reversed-phaseoctadecyl column (Lichrosorb RP-18, Alltech Associates, Inc., Deerfield,IL), and a single wavelength detector (Model 153, Altex Scientific) setat 280 nanometers. Chromatograms were recorded at a chart speed of 0.5centimeters/minute. The mobil phase was 30% methanol in 0.01 molaracetic acid, pumped at a flow rate of 1.5 milliliters per minute.Concentrations were determined by the method of peak height ratios.

The results of this study are shown in the graph of FIG. 9. The value ateach time point represents the mean of five determinations.

As can be seen from examination of FIG. 9, the blood level ofchlorothiazide provided by the composition of this invention (study) washigher than that provided by either of the control compositions over thefirst six hours after administration, with the peak time for drug inplasma being at about eight hours for the composition of this inventionand for control I, but nearer to six hours for the powdered drug(Control II). It is also readily seen that the composition of thisinvention provided a bioavailability of about two times (1.95±0.14) theamount of treating agent to the blood from about eight hours afteradministration through the remainder of time during which data weretaken.

A study of the passage of gastrointestinal transit of albumin head andof bioadhesive, polycarbophil-albumin bead dosage forms was alsoconducted using the beads described in this Example and the surgicalprocedures described in Example 3. The number of beads found in thestomach and small intestines of the treated rats were counted at a timesix hours after surgical administration of the beads.

The results of this study showed that almost 90 percent of thebioadhesive-albumin beads of this invention remained in the stomachafter six hours, with very few beads being found beyond the stomach. Inthe absence of the bioadhesive, the majority of the albumin beads movedat least half-way down the small intestine, with some moving further.Practically no bioadhesive-free albumin beads were found in the stomachafter six hours.

The above results clearly illustrate the efficacy of a composition ofthis invention in an in vivo system. While the release of chlorothiazidefrom the albumin beads in vivo was relatively rapid, the duration ofaction and the bioavailability of the chlorothiazide was significantlyimproved over that obtained with a typical sustained release dosageform. The basis for that improvement demonstrated in this study is thereduced rate of a gastric emptying and subsequent increase in contacttime of the bioadhesive-albumin dosage form as compared to a typicalsustained release, albumin bead, dosage form. That delay in stomachemptying is caused by the binding of the bioadhesive to the beads and tothe gastric mucin/epithelial cell surface.

Example 10

Controlled Release Ophthalmic Treatments

An aqueous mixture of ¹⁴ C-labeled fluorometholone as treating agent andpolycarbophil as bioadhesive was prepared. The ¹⁴ C-labeledfluorometholone was thereby sorbed into the bioadhesive particles. Theparticles so prepared were filtered, dried, crushed and screened toprovide a ¹⁴ C-labeled fluorometholone-containing particulatecomposition of this invention.

The composition so prepared was resuspended in water (study), andanother aqueous composition containing ¹⁴ C-labeled fluorometholone, butno bioadhesive (control) was also prepared. The thus preparedcompositions were separately instilled into the precorneal pockets ofseparate rabbits. The radioactivity present in the corneas and aqueoushumors of the treated rabbits was measured at various times afteradministration and resulting contact of the study and controlcompositions with the mucosa of the eye.

The results of this determination showed that the composition of thisinvention provided a higher concentration of the treating agent in bothtissues as well as a prolongation of the presence of the treating agentin both tissues. These results provide yet another example of the invivo effficacy of a composition of this invention.

Example 11

Controlled Release Opthalmic Composition

Another controlled release composition of this invention was prepared inwhich the treating agent, fluorometholone, was entrapped within thebioadhesive during the polymerization of the bioadhesive. Here, 0.133grams of fluorometholone was premixed with 20 grams of acrylic acid,0.03 grams of 2,5-dimethyl-1,5-hexadiene and 0.2 grams of benzoylperoxide.

The mixture so prepared was then added with stirring to a refluxingaqueous composition containing 160 grams of MgSO₄ -7H₂ O, andpolymerization, recovery, drying of the resulting treatingagent-containing bioadhesive particles was carried out following thegeneral procedures discussed in Example 1. The dried composition of thisinvention so prepared was then crushed and sieved to provide particlesthat pass throught a 100 mesh sieve screen (U.S. Standard Sieve Series).

The particles so prepared were then added to a saturated aqueoussolution of fluorometholone as a further composition of this inventionsuitable for contacting opthalmic mucosa. The use of a saturatedsolution of the treating agent in conjunction with a composition of thisinvention containing the same treating agent tends to retard prematurerelease of the treating agent from the composition into thephysiologically tolerable carrier in which the composition is suspended.

Example 12

Bioadhesion as a Function of pH Value

The force measured to separate a bioadhesive polymer that is thereaction product of the polymerization of acrylic acid with 0.3 weightpercent of 3,4-dihydroxy-1,5-hexadiene that had a density of 1.56 g/ccis shown in FIG. 10. As is seen from the Figure, the maximum adhesionwas observed at a pH value of about 5 to about 6. That maximum vaue wasmore than twice the adhesive force required for the separation at pHvalues of 0.46, 1.42 or 2.0. As is also seen, adhesion provided by thatbioadhesive polymer was substantially reduced at pH value of 7. Thatreduction was statistically significant in a Student's t-test, p lessthan 0.01. Bioadhesive forces were measured as discussed previously inExample 2.

The foregoing is intended as illustrative of the present invention butnot limiting. Numerous variations and modifications may be effectedwithout departing from the true spirit and scope of the novel conceptsof the invention.

What is claimed is:
 1. A controlled release treatment compositionincluding a bioadhesive and an effective amount of fluorometholone, saidbioadhesive comprising a water-swellable, but water-insoluble, fibrous,cross-linked carboxy-functional polymer, said polymer sized to passthrough a 100 mesh sieve screen, U.S. Standard Sieve Series, andcontaining (a) a plurality of repeating units of which at least about 80percent contain at least one carboxyl functionality, provided bypolymerized acrylic acid or methacrylic acid and (b) about 0.05 to about1.5 percent cross-linking agent substantially free from polyalkenylpolyether, said percentages being based upon the weights ofunpolymerized repeating unit and cross-linking agent, respectively. 2.The controlled release composition of claim 1 wherein said bioadhesiveand said flurometholone are intimately admixed.
 3. The controlledrelease composition of claim 2 wherein said flurometholone is present asa saturated solute in a physiologically acceptable aqueous carrier. 4.The controlled release composition of claim 1 wherein said carboxylfunctionality is provided by polymerized acrylic acid.
 5. The controlledrelease composition of claim 4 wherein at about 90 percent of saidrepeating are polymerized acrylic acid.
 6. The controlled releasecomposition of claim 4 wherein said bioadhesive is a reaction product ofthe polymerization of acrylic acid and said cross-linking agent.